Accuracy of virtually planned and conventionally placed implants in edentulous cadaver maxillae and mandibles: a preliminary report.

STATEMENT OF PROBLEM: The accuracy of mental navigation is thought to depend on the clinician's spatial ability. Mental navigation, therefore, is associated with deviations between the mental plan and the definitive implant position. To learn more about the deviation that might occur, it is important to evaluate the accuracy of mental navigation during placement of implants. PURPOSE: The purpose of the study was to compare accuracy outcomes between virtually planned and conventionally placed implants, and among surgeons with varying experience. MATERIAL AND METHODS: Five completely edentulous sets of maxillae and mandibles from human cadaver heads were scanned by computed tomography. Five surgeons planned and placed 60 implants into these jaws, and accuracy was analyzed for 4 parameters: coronal and apical positions, angulation, and depth. The preoperative and postoperative computed tomographies were aligned in voxel-based registration software, which allowed comparison between virtually planned implant positions and actual implant positions. Data were analyzed with the t test (α=.05), ANOVA, and the Scheffé test. RESULTS: Mean (standard deviation) values were as follows: apex, 2.33 ±1.20 mm (range, 0.51-6.31 mm); coronal, 1.88 ±1.02 mm (range, 0.2-5.0 mm); angle, 7.34 ±3.62 degrees (range, 0.19-16.57 degrees); and depth, 0.03 ±1.15 mm (range, -3.47 to 2.10 mm). The apex and coronal position and the angle differed significantly between the virtually planned and actually placed implants. Significant between-surgeon differences were found in implant depth and coronal position. The apex and coronal positions differed significantly between the upper and lower jaw, with better performance achieved in the upper jaw. CONCLUSIONS: The results found statistically significant differences between the virtually planned and conventionally placed implants and among the 5 surgeons.

A retrospective cohort study of 113 patients rehabilitated with immediately loaded maxillary cross-arch fixed dental prostheses in combination with immediate implant placement.

PURPOSE: To retrospectively evaluate the outcome of immediately loaded cross-arch fixed dental prostheses 6 months after loading. A second aim was to compare survival rates of implants placed in healed versus fresh extraction sites. MATERIALS AND METHODS: In total, 113 consecutive patients about to have their maxillae rendered fully edentulous (mean extractions per patient: 6.7 teeth) received four to eight implants each (total number = 675) which were immediately placed in healed sites (323 implants, 47.9%) or fresh sockets (352 implants, 52.1%). Immediate loading of provisional prostheses was performed and all patients were followed up for 6 months. The success criteria included prosthesis success, assessment of individual implant stability and complications. RESULTS: No patients dropped out and all 113 patients received definitive fixed prostheses after 6 months of loading. The overall implant survival rate after 6 months was 99.1%. Six implants were lost in 6 patients (5.3%). Five of them were inserted in fresh extraction sockets (1.4%) and one in a healed site (0.3%). No significant difference (P = 0.1621) was found for implants placed in healed sites versus fresh extraction sites. Ten patients had fractures of the provisional prostheses as complications. CONCLUSIONS: Immediate implant placement and loading resulted in high implant as well as prosthetic survival rates. Placement in healed or fresh extraction bone sites may not influence implant survival.

A retrospective cohort study of 105 patients rehabilitated with immediately loaded mandibular cross-arch bridges in combination with immediate implant placement.

PURPOSE: To evaluate the outcome of immediately loaded cross-arch bridges 4 months after loading. A second aim was to compare survival rates of implants placed in healed versus fresh extraction sites. MATERIALS AND METHODS: In total, 105 consecutive patients about to have their mandibles rendered fully edentulous (mean extractions per patient: 6.1 teeth) received four to six implants each (total number = 448), which were immediately placed in healed sites (266 implants, 59%) or fresh sockets (182 implants: 41%). Immediate loading of provisional prostheses was performed and all patients were followed-up for 4 months. The success criteria included prosthesis success, assessment of individual implant stability and complications. RESULTS: No patient dropped out and all 105 patients received definitive fixed prostheses after four months of loading. The overall implant survival rate after four months was 98.2%. Eight implants were lost in eight patients (8%). Four of them were inserted in fresh extraction sockets (2.2%) and four in healed sites (1.5%). No significant difference (P = 0.4990) was found for implants placed into healed sites versus fresh extraction sites. No complications were reported. CONCLUSIONS: Immediate implant placement and loading resulted in high implant as well as prosthetic survival rates. Placement in healed or fresh extraction bone sites did not influence implant survival.

Virtual variation simulation of CAD/CAM template-guided surgeries performed on human cadavers: Part II.

STATEMENT OF PROBLEM: CAD/CAM template-guided surgery has gained attention as a method of improving the predictability of dental implant placement. However, due to possible variations during the manufacturing process and in the robustness of the template design, a virtual prediction of the potential positioning of the implants is needed. PURPOSE: The purpose of this study was to perform virtual variation simulations on virtually planned implant placements and to compare them with corresponding results from actual surgeries performed on human cadavers in a previous study. MATERIAL AND METHODS: Seventeen computer-aided plans were used for virtual variation simulation of surgeries conducted on 17 human cadavers and 145 implants placed in the cadavers. For each surgery, 10,000 virtual surgeries were performed, resulting in 1,450,000 implant placements. The results from the virtual variation simulations were statistically compared with the results from the actual surgeries. The Mann-Whitney U test was used to compare the implant distributions (alpha=.05). RESULTS: In the maxillae, the difference between the simulated average mean of the mean and the compared surgical average of the median was 0.22 mm (apex) and -0.35 mm (hex), and for the mandible, the corresponding values were -0.19 mm (apex) and -0.69 mm (hex). The simulated average mean of the range compared to the mean range of the maximum deviation results from the surgeries of the maxillae was 2.96 mm (apex) and 0.44 mm (hex), and 2.3 mm (apex) and 0.26 mm (hex) for the mandible. The implant distributions between the simulations and the surgeries were significantly different at both the hex (P<.001) and apex (P<.001). CONCLUSIONS: The implant distributions were neither static nor normally distributed. Thus, within the limitations of this study, the definitive geometrical variations of the implants were not static, as they depend on the individual anatomy of the jaws and the ability to place the CAD/CAM-guided surgical template in the proper position.

Guided surgery and presurgical prosthesis: preliminary results of 33 fully edentulous maxillae treated in accordance with the NobelGuide protocol.

OBJECTIVE: The aim of this study was to present the preliminary results of 33 edentulous maxillary patients treated using the Nobelguide (Nobel Biocare AB, Göteborg, Sweden) technique. MATERIALS AND METHODS: Thirty-three patients were treated according to the conventional protocol of the Nobelguide technique in two clinical centers. This group of patients received 211 implants. Monitoring was carried out for over 12-51 months, depending on the patient. The Nobelguide protocol was used for all patients. RESULTS: Of the 211 implants loaded, four were lost (1.9%). The implant survival rate was therefore 98.1%. The prosthetic survival rate was 100%. There were some per-operative complications (four) and some postoperative complications (10 fractures of resin). CONCLUSION: These preliminary results seemed rather promising. These were the first cases of experienced surgeons who needed to learn a new implant placement protocol. It was clear that analysis and understanding of the system were essential in order to obtain such a success. Only one implant was replaced without there being any impact on the prosthesis survival rate which is 100%.

Accuracy of CAD/CAM-guided surgical template implant surgery on human cadavers: Part I.

STATEMENT OF PROBLEM: An optimal method for approaching the clinical surgical situation, when using preoperatively, virtually planned implant positioning, is to transfer data to a CAD/CAM-guided surgical template with the definitive position of the implant placed after surgery. The accuracy of CAD/CAM-guided surgeries must be determined to provide safe treatment. PURPOSE: The purpose of this study was to compare the deviation between the position of virtually planned implants and the position of implants placed with a CAD/CAM-guided surgical template in the mandible and the maxilla in human cadavers. MATERIAL AND METHODS: Ten maxillae and 7 mandibles, from completely edentulous cadavers, were scanned with CT, and 145 implants (Brånemark RP Groovy) were planned with software and placed with the aid of a CAD/CAM-guided surgical template. The preoperative CT scan was matched with the postoperative CT scan using voxel-based registration. The positions of the virtually planned implants were compared with the actual positions of the implants. Data were analyzed with a t test (alpha=.05). RESULTS: The mean measurement differences between the computer-planned implants and implants placed after surgery for all implants placed were 1.25 mm (95% CI: 1.13-1.36) for the apex, 1.06 mm (95% CI: 0.97-1.16) for the hex, 0.28 mm (95% CI: 0.18-0.38) for the depth deviation, 2.64 degrees (95% CI: 2.41-2.87) for the angular deviation, and 0.71 mm (95% CI: 0.61-0.81 mm) for the translation deviation. CONCLUSIONS: The results demonstrated a statistically significant difference between mandibles and maxillae for the hex, apex, and depth measurements in the variation between the virtually planned implant positions and the positions of the implants placed after surgery with a CAD/CAM-guided surgical template.